High tension air blast circuit breakers with a plurality of series connected breaking gaps per pole



Jan. 23, 1962 R. SCHULZ 3,018,352

HIGH TENSION AIR BLAST CIRCUIT BREAKERS WITH A PLURALITY 0F SERIESCONNECTED BREAKING GAPS PER POLE Filed Sept. 29, 1959 3 Sheets-Sheet 1EN 27 2s 2s I a 1 8 i I VENTOR.-

Fir/Gard 5 (22112 fiffomey.

Jan. 23, 1962 R. SCHULZ 3,018,352

HIGH TENSION AIR BLAST CIRCUIT BREAKERS WITH A PLURALITY OF SERIESCONNECTED BREAKING GAPS PER POLE Filed Sept. 29. 1959 5 Sheets-Sheet 2 L5 so INVENTOR. .Kr/zard 50'' [Z Jan. 23, R. SCHULZ HIGH TENSION AIRBLAST CIRCUIT BREAKERS WITH A PLURALITY OF SERIES CONNECTED BREAKINGGAPS PER POLE Filed Sept. 29, 1959 15 Sheets-Sheet 3 Fig.3

I VENTOR. Flt/10rd 5c uZZ United States Patent M 3,018,352 HIGH TENSIONAIR BLAST CIRCUIT BREAKERS WITH A PLURALITY 0F SERIES CONNECTED BREAKINGGAPS PER POLE Richard Schulz, Friedberg, Hessen, Germany, assignor toAllmiinn-a Svenska Elektriska Aktiebolaget, Vasteras, Sweden, acorporation of Sweden Filed Sept. 29, 1959, Ser. No. 843,130 Claimspriority, application Germany Oct. 10, 1958 2 Claims. (Cl. 200148) Inhigh tension air blast circuit breakers having a plurality of seriesconnected breaking gaps per pole, arrangements must be made by which therecovery voltage upon a breaking is distributed as equally as possibleover the separate breaking gaps of the breaker pole. For this purposeohmic resistances are suited, which damp the over voltages which aregenerated upon interruption of a power line or a transformer operatingat no load. The more low-ohmic these resistances and the higher theresidual current flowing through the resistances after an opening of themain breaking gap, the more effectively are the over-voltages dampened.

In circuit breakers which operate without a series connected switch, itis necessary to interrupt the residual current through the resistancesby auxiliary breaking gaps, the contacts of which open a short timeafter the main breaking gaps. In air blast circuit breakers this delayis generally caused by pneumatic arrangements. The auxiliary breakinggaps are often designed like spark gaps and the residual current isextinguished by the contacts being drawn apart in a container filledwith compressed air. If, however, the residual currents through theresistances are high, it will be necessary to subject the auxiliarybreaking gaps to blast air. Such arrangements are known. In an air blastcircuit breaker, the main breaking gaps of which in operation arepermanently arranged in compressed air, it has been suggested to use thedecrease in pressure which occurs upon an opening of the main breakinggap, for subjecting the auxiliary breaking gaps to a blast of compressedair by an arrangement according to which compressed air in a limitedspace is allowed to flow into the space containing compressed air oflower pressure so that the auxiliary breaking gaps are subjected toblast air. This device has the disadvantage that the gases ionized inthe auxiliary breaking gap flow to the main breaking gap at its nearestpoint and these may cause the main breaking gap to be re-ignited.

Another device according to which the extinguishing gases from theauxiliary breaking gap flow out through the main blast valve has thedisadvantage that the blast valve with its comparatively large area offlow must be held open until the residual current through the auxiliarybreaking gap has also been safely interrupted. This, however, means anundesirable, high consumption of compressed air and makes it necessaryto use large compressed air containers.

The invention avoids these disadvantages and relates to a device for airblast circuit breakers with a plurality of series connected mainbreaking gaps per pole and each main breaking gap connected in parallelwith a resistance and an auxiliary breaking gap, by which comparativelyhigh residual currents may be interrupted with an unusually lowconsumption of compressed air.

The invention is characterized in that a passage is provided leadingpast the auxiliary gap to free air, with a blast valve in the passagewhich is closed shortly after the passage is open to free air by thepressure in the container, and that the valve which controls the openingof the passage also serves for connecting the passage to the interior ofthe container.

The contact of the auxiliary breaking gap, which contact is connected toa piston, can suitably be movably 3,618,352 Patented Jan. 23, 1962 ICCarranged in a piston housing. By venting the space enclosing the pistonhousing, upon a breaking action, first the contact with its piston ismoved and then the piston housing, because of the influence of thecompressed air in the extinguishing chamber. The piston housing closesthe outlet opening for the compressed air in its end position while thecontact with its piston is returned to its primary position in thepiston housing. While the spring, which upon a breaking action has beenset by the movement of the piston housing, is held set by the influenceof the compressed air in the extinguishing chamber, the holding force isneutralized upon a closing action by the supply of compressed air on theback of the piston housing and the piston housing is returned by thespring force to its primary position, so that the auxiliary breaking gapis closed. If the auxiliary breaking gap is subjected to comparativelyhigh voltages, the opening for the movable contact in the piston housingis suitably designed as an insulating nozzle.

The invention will be more easily understood with reference to theaccompanying drawings. FIGURE 1 shows the main breaking gap and theauxiliary breaking gap built together. FIGURE 2 shows the auxiliarybreaking gap and its operating mechanism when the auxiliary breaking gapis closed. FIGURE 3 shows the auxiliary breaking in an intermediateposition and FIG- URE 4 the auxiliary breaking gap in an open endposition. 1 designates an extinguishing chamber filled with compressedair, which chamber is supported by a pillar insulator, not shown, and inwhich chamber the stationary contact 2 and the movable contact 3 havebeen arranged. The resistance 4 with the auxiliary breaking gap 5, 6 isconnected in parallel with the main breaking gap 2, 3. The movablecontact 3 of the main breaking gap, which contact is held in closedposition by the spring 7, is controlled by the compressed air which, foran opening action, is supplied through the pipe 8. Upon this the piston9 and the diiterential piston 10 are moved to the left, the valve 11 isclosed and the blast valve 12 is opened. Through the latter thecompressed air in the chamber may flow through the breaking gap 2, 3 at13 to the open air. The valve 11 closes the channel 14 and at the sametime causes the space 15 to be connected to the open air. The contact 3of the main breaking gap is moved to the right and the are generated issubjected to a blast of pressure air and is extinguished. The channel 16in the differential piston 10 after some time causes the pressure onboth sides of this piston to be equalized so that the piston 10 underthe influence of the spring 17 and the movement of the contact 3, isreturned to its initial position and the blast valve 12 is closed again.The compressed air in the space 1 holds the movable contact 3 in openposition counter-acted by the spring 7. The piston 18 connected to themovable contact 3 then rests against the smaller surface of thediiterential piston 10 and closes the blast valve 12.

FIGURE 2 shows the auxiliary breaking gap 5, 6 connected in parallel tothe main breaking gap 2, 3. A piston 19 is connected to the movablecontact 5 of the auxiliary breaking gap, which piston undercounteraction of a spring 21 can be moved in the piston housing 20. Thepiston housing 20 is biased by a spring 22 and is arranged in the space23, which through the openings 24 communicates with the pipe 25. Thepipe 25 is, as FIG- URE 1 shows, connected to the stop valve 26, throughwhich the pipe 25 can be connected either to the container 1 or, throughthe opening 27, to the open air. The valve piston 28 is controlled bythe pressure in the pipe 8. When the main breaking gap is closed, asFIG- URE 1 shows, the pipe 8 is not filled with compressed air. The pipe25 now communicates with the extinguishing chamber 1 and is consequentlyfilled with compressed air, so that the piston housing 20 and thecontact 5 are held in closed position by the spring 22. 29 designatesthe nozzle rigidly connected to the piston housing 20, which nozzle maybe designed as an insulating nozzle and has an opening therein for themovable contact.

FIGURE 1 shows the auxiliary gap in closed position. If the pipe 8 issupplied with compressed air, the main breaking gap is opened and,immediately after, the valve head 28 is moved to the left, whereby thepipe 25 is emptied through the opening 27. The consequence is that thecompressed air in the chamber 1 acts through the openings 30 on thepiston 19 and moves this upwards against the counter-action of thespring 21 until the piston meets the pin 31 in the piston housing 20(FIGURE 3).

The generated arc is, during the course of this, extinguished in thenozzle 29. Due to the influence of the compressed air the piston 19 withthe contact 5 and the piston housing 20 is moved further upwards so thatthe spring 22 is compressed. The extinguishing gases from the auxiliarybreaking gap flow through the channels 30, 32, 33 and the openings 24(FIGURE 4) into the pipe 25 and out to the open air. In the upperposition of the piston housing 20, the opening 35 and by that theopenings 24, are closed by blast valve 34 seating over opening 35 sothat in this position the compressed air is kept from flowing out to theopen air. The pressure on both sides of the piston 19 has now beenequalized through the channels 32 so that the spring is able to move themovable contact 5 of the auxiliary breaking gap closer to the stationarycontact 6 while maintaining a sufficient insulating distance.

Upon a closing action, the piston housing 20 with the valve head 34 isinfluenced, through the pipe 25, by compressed air so that the spring 22moves the piston housing downwards and the auxiliary breaking gap isclosed. At this the movement is dampened due to the air in space 23being compressed -I claim:

1. A high tension air blast circuit breaker comprising a container forcompressed m'r, a main breaking gap, a resistance and an auxiliarybreaking gap connected in series with each other and in parallel withthe main breaking gap, means forming a passage extending from thecontainer past the auxiliary gap to free air, blast valve means in saidpassage on the opposite side of the auxiliary gap from the containeroperable by the pressure in the container to close the passage afterconnection of the passage to free air, and stop valve means forselectively connecting the part of the passage on the opposite side ofthe blast valve from the container to free air and to the container,said auxiliary breaking gap having a movable contact, a movable pistonhousing rigid with the blast valve, a piston movably arranged in saidhousing and rigid with the movable contact, said contact and piston,when said part of the passage is connected with free air, being movedrelative to said housing to open the auxiliary breaking gap and meansfor returning said contact and piston to their original position in thehousing when said blast valve is closed.

2. A high tension air blast circuit breaker according to claim 1, inwhich the piston housing is provided with an opening for the movablecontact, said opening being shaped like a nozzle, the portion of thehousing forming the nozzle being of insulating material.

References Cited in the file of this patent UNITED STATES PATENTS2,747,055 Forwald May 22, 1956 2,786,117 Forwald Mar. 19, 1957 2,786,119Forwald Mar. 19, 1957 2,908,788 Forwald Oct. 13, 1959 FOREIGN PATENTS167,384 Australia Apr. 6, 1 956

